The Effect of the Compatibilization Route of PA/PO Blends on the Physico-chemical Phenomena Developing Along a Twin-screw Extruder Ana Vera Machado, * 1 Virginie Yquel, 1,2 Jose´Antonio Covas, 1 Jean-Jacques Flat, 2 Nessim Ghamri, 2 Andreas Wollny 2 Summary: The effect of the compatibilization method (ex-situ, in-situ, cross linking) on the chemical conversion, morphological and rheological evolution of polyamide/ polyolefin blends along a twin screw extruder is investigated. For this purpose, samples were quickly collected from the extruder at specific barrel locations, quenched and subsequently characterized off-line. While significant changes occur very quickly in the melting zone for the ex-situ and in-situ routes, changes of the cross linking system could be detected along all the extruder. Correlations between chemical conversion, particle size and linear viscoelastic response could be estab- lished. Keywords: blends; compatibilization; particle size distribution; reactive extrusion; rheology Introduction Although it is currently normal practice to prepare new materials with innovative properties by blending existing polymers, rather than by searching for new mono- mers, this route faces practical difficulties as most promising polymer pairs are thermo- dynamically immiscible. The incorporation of a compatibilizer (also known as inter- facial agent, or emulsifier), usually a graft or block copolymer, is therefore necessary to reduce the interfacial tension, enhance the adhesion at the interface, facilitate the dispersion of one phase in the other and stabilize the morphology [1–3] . Compatibilization can be achieved (a) ex-situ, by addition of a pre-synthesized copolymer to the components, b) in-situ, by creating a copolymer during blend prepara- tion which is located at the interface between the two components and c) by stabilizing the dispersed phase via dynamic vulcanization, or cross linking. Ex-situ compatibilization provides the opportunity for controlling more easily the molecular architecture of the copolymer. However, not only it requires specific chemical routes and reaction conditions (when possible), but when the compatibilizer is added to the blend components it is difficult to ensure that most of it actually goes to their interface. In-situ (or reactive) compatibili- zation requires that both polymers have reactive groups at the interface. For example, terminal amine groups of PA6 can react with maleic anhydride groups of a modified polyolefin. Since the reaction takes place at the interface, the process is very effective, although it is difficult to control the rate of formation, as well as the amount and molecular architecture of the compatibiliser. Finally, cross linking of a given material during mixing (dynamic vulcanization) determines the dispersed phase and guarantees stable size and shape during subsequent thermomechanical cycles [1,3] . All above methods have been widely used to obtain compatibilized immiscible Macromol. Symp. 2006, 233, 86–94 DOI: 10.1002/masy.200650111 86 1 University of Minho, Campus Azurem, 4800-058 Guimaraes, Portugal Fax: (þ351) 253510339 E-mail: avm@dep.uminho.pt 2 ARKEMA, Cerdato, 27 470 Serquigny, France ß 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim